1. Field of the Invention
The present invention relates to a magnetic disc device for use in writing and reading information to and from a magnetic disc medium and, in particular, to a magnetic head device having a head control mechanism for effecting head contact during high speed medium rotation.
2. Description of the Related Art
Recently, a magnetic disc device has been developed which is capable of recording and reproducing data on and from both a large capacity medium and a low capacity (downward compatibility) medium. In such a device, the heads are provided with a gap for large capacity and a gap for low capacity (downward compatibility), switching between the heads being appropriately effected.
FIG. 6 shows a disc D and heads 4 and 5 in a conventional magnetic disc device 20.
In the medium of this magnetic disc device 20, the disc D is accommodated in a hard case (not shown), and when the medium is inserted into the device, a shutter provided in the hard case is opened and the disc appears, and the heads enters through the shutter to come into contact with the surfaces of the disc D, making it possible to record and reproduce data.
As shown in FIG. 6, in this conventional magnetic disc device 20, the heads 4 and 5 are opposed to either surface of the disc D, and the heads 4 and 5 are movable in the radial direction of the disc D. In the head 4 on side 0 (the side on which the position of opposition to the disc D is determined), a gap 4b for downward compatibility is formed on the inner side of the disc D, and a gap 4a for large capacity is formed on the outer side thereof. In the head 5 on side 1 (the side on which the head makes a movement to and away from the disc D), a gap 5b for downward compatibility is formed on the outer side, and a gap 5a for large capacity is formed on the inner side.
When the medium is inserted to a predetermined position, the head 5 first comes into contact with the lower surface of the disc D, and then the disc D starts to rotate, and further, the head 4 comes into contact with the upper surface of the disc D. It is determined whether the inserted medium is a large capacity medium or a downward compatibility medium. In the case of a large capacity medium, the disc D rotates at high speed, and in the case of a downward compatibility medium, the disc D rotates at low speed.
The above-described conventional magnetic disc device has the following problems.
When the medium is inserted to reach a predetermined position, the head 5 first comes into contact with the lower surface of the disc D. After that, the disc D rotates, and further, the head 4 comes into direct contact with the data zone 6a of the disc D. When the medium inserted is one for downward compatibility, the disc D rotates at low speed when the head 4 comes into contact with the disc, and when the medium inserted is one for large capacity, the disc D rotates at higher speed.
In this way, when a medium for downward compatibility is inserted, the disc D rotates at low speed, so that there is little fear of damaging the disc D even when the heads 4 and 5 are brought into direct contact with the data zones 6a and 6b. However, when a medium for large capacity is inserted, the disc D rotates at high speed, so that when the head 4 is loaded onto the disc D in this condition, there is a fear that the data zone 6a will be damaged since the contact is effected directly in the data zone 6a. As a result, it is impossible to record and reproduce data, or the data recorded may be damaged.
It might be possible to adopt a means for rotating the disc D after the heads 4 and 5 are brought into contact with the disc D. However, when the rotation is started after the heads have been brought into contact with the disc D, the durability of the disc D is deteriorated. Further, the heads 4 and 5 are attracted by the disc D to thereby damage the disc D.
The present invention has been made with a view toward solving the above problems. It is an object of the present invention to provide a magnetic disc device capable of minimizing damage to the medium when head loading is effected.
According to the present invention, there is provided a magnetic disc device of the type which includes a medium having on both sides data zones deviating from each other, and heads which are opposed to the sides of the medium and whose head gaps are offset, the heads consisting of a first head whose position of medium opposition is fixed and a second head which is caused to move to and away from the medium,
the magnetic device comprising a head control mechanism which causes a slide surface of the second head to come into contact with a portion deviating from the data zone, with the first head being in contact with the data zone.
In the above means, when, for example, the head is controlled on the inner side of the medium, when the medium is inserted into the magnetic disc device and reaches a predetermined position, the slide surface of the first head, that is, the head on the side of the data zone further offset to the inner side, comes into contact with the disc, and then the slide surface of the second head comes into contact with the disc. At this time, the slide surface of the second head comes into contact with a portion offset from the data zone. Thus, when the second head comes into contact with the disc, it is possible to prevent as much as possible the slide surface from damaging the disc. In particular, when the medium is large capacity type, the rotation is effected at higher speed to record and reproduce data than in the case of a medium for downward compatibility, so that the disc is more subject to damage. However, due to the above means, it is possible to prevent as much as possible the medium from being damaged even in the case of a large capacity type medium.
Further, the above-mentioned heads can form gaps in conformity with writing and reading to and from a small capacity medium and a large capacity medium.
For example, in this case, the gaps of the heads are offset, and in parallel with respect to the radial direction of the medium. When the first head has a downward compatibility gap on the head outer side and a large capacity gap on the head inner side, the second head has a large capacity gap on the head outer side and a downward compatibility gap on the head inner side.
Further, the head control mechanism comprises an arm which supports the second head and biases it in the direction of the medium, and a support member which supports the arm at a position where the second head is separated from the medium, and when the arm and the head move, the head is preferably separated from the support member and comes into contact with the medium.
For example, when the medium is inserted into the device by the above means, the second head is supported by the arm supporting the head and biased in the direction of the medium, the head being supported by the support member directly before the head comes into contact with the medium. Further, due to the movement of the arm, the head gradually moves in the direction of the medium, and the head, that is, the slide surface of the head comes into contact with the surface of the disc. As a result, the head is prevented from coming into contact with the medium abruptly and with larger force, thereby preventing as much as possible the medium from being damaged.
In this case, the configuration of the support member can be appropriately changed according to the configuration of the arm coming into contact with the support member. For example, it is possible to provide on the arm side a supported portion which is pin-like with respect to the arm width direction, and provide on the support member side a member supporting the supported portion. Or, it is possible to integrally provide at the forward end of the arm a small-piece-like supported portion and support it by the support member.
Further, the upper surface of the support member is formed by an inclined surface which is downwardly directed on the rear side with respect to the direction in which the arm advances, and the inclined surface is formed by a slope which is gentler on the upstream side than on the downstream side with respect to the rotating direction of the medium, and when the arm retreats, the head is preferably formed such that it is moved onto the medium in a position in which it is upwardly inclined on the upstream side.
Due to the above means, when the head comes into contact with the medium, the head is inclined, and the medium is prevented from being damaged as a result of the head coming into contact with the upstream side portion of the medium with respect to the medium rotating direction.
For example, when the pin-like supported portion is provided, it is possible to form the inclined surface of the support member such that the slope is gentler on the upstream side than on the downstream side with respect to the medium rotating direction. Or, when a small-piece-like supported portion is provided at the forward end on the arm side, the supported portion can be formed such that it is offset to the upstream side from the center of the head with respect to the medium rotating direction.